Industry’s First Thunderbolt 2 RAID Posts Impressive Speeds at an Affordable Price

Promise’s Pegasus2 R8 is an eight-drive, Thunderbolt-native RAID that’s currently the fastest in the industry, thanks to its early adoption of the same Thunderbolt 2 ports that recently started shipping on Apple’s newest Macbook Pro laptops and the new Mac Pro workstation, and is due soon on a few PCs. At $3,599 for 24TBs, the Pegasus2 is also the most affordable eight-drive RAID I’ve seen yet.

You’ll start seeing other Thunderbolt 2 RAIDs soon, but for now, the Pegasus2 has the territory all to itself, which translates into impressive performance. For instance, I ran Blackmagic’s Disk Speed Test app on my R8 in a RAID 5 configuration (one-drive redundancy), and got reads of around 900 MB/s and writes of 850 MB/s. Tests with AJA’s System Test app were similar. Either way you test it, that’s fast enough to handle any kind of video format you throw at it (and often many, many streams of popular formats), including 4K variants.

Of course, the Pegasus2’s speedy read and write scores still aren’t nearly as fast as you might expect from Thunderbolt 2’s 20Gb/sec throughput, which translates to roughly 2500 MB/s. But no eight-drive RAID based on spinning hard drives will ever get close to that high-falutin’ speed. For starters, even working together in a RAID, the Pegasus2’s eight 7200 rpm hard drives can only read/write data so fast. Secondly, running the Pegasus2 in its default RAID 5 configuration keeps one of the 8 drives for redundancy, which gives you only 7 drives contributing to high speeds. And, of course, I can’t remember the last technology that ever met its theoretical maximum speed in the real world. Oh well.

At any rate, for an eight-drive RAID based on spinning hard drives, the Pegasus2 is as fast as they come — and still significantly faster than an eight-drive RAID based on the old-school Thunderbolt 1 port. To see how much of an improvement Thunderbolt 2 offers, I connected the Pegasus2 to my spiffy new 6-core Mac Pro, but using an older Thunderbolt 1-based La Cie drive as a middleman. That daisy-chain configuration forced the Pegasus2 to run at Thunderbolt 1 speeds, and the Blackmagic app reported a read of about 750 MB/s and a write of about 620 MB/s. So Thunderbolt 2 appears to give you roughly an extra 150–230 MB/sec of bandwidth over the original Thunderbolt.

Using Thunderbolt 2 also means that you can daisy-chain other super-fast Thunderbolt 2 devices off of the Pegasus2 (it has two Thunderbolt 2 ports) and those devices will tap into to the same 20 Gb/sec throughput that the RAID enjoys.

Day-to-Day Use

I had about 3 weeks to use the Pegasus2 in a variety of real-world editing scenarios. Here are some things to consider as you evaluate the drive for your own work:

•   The Pegasus2 is very easy to set up. There are no drivers to install, and it comes out of the box configured as a RAID 5 (again, one drive held in redundancy). Once connected via Thunderbolt, it shows up on your desktop as a single big, fast volume.

•   One tip for setup, though: When you boot the R8 for the very first time, it runs at slightly reduced speed as it finishes “syncing”, which is a one-time process. So don’t immediately do a Blackmagic or AJA speed test or you’ll be a little disappointed. The process lasts several hours.

•   There’s a power button on the front of the unit, but you generally don’t need to use it since the RAID automatically turns itself on whenever you boot up or wake your Mac from sleep, and it turns itself off whenever you you shut down or sleep your computer. That’s very convenient, unless there are times you don’t want an eight-drive RAID sucking up power, in which case you can use the power button to manually turn it off.

•   Operation is on the quiet side. I had the RAID about eight feet away using a long Thunderbolt cable and could hear a low-pitched hum, but nothing too obtrusive. I would say the Pegasus2 is a little louder than a last-generation Mac Pro, but not by much. The RAID comes with a one-meter cable, but you can minimize noise by buying a three-meter cable for less than $50 these days. (A good source for cables is Other World Computing.)

•   My Pegasus2 shipped with “desktop” Seagate drives instead of more robust “enterprise” drives. Enterprise drives are rated for higher stress levels than desktop drives and are warrantied for at least five years, whereas desktop drives typically have two-year warranties (Promise warranties both the Pegasus enclosure and drives for two years). Does it really matter? From a cost standpoint, enterprise drives would certainly make the R8 appreciably more expensive. As for reliability, I can’t offer scientific evidence, but I do recall reading a fair number of Pegasus1 user reviews complaining of bad drives over the last couple of years (Apple’s online store has taken down those reviews since it no longer sells the old Pegasus RAIDs, but you can still find some on Anecdotally, I can also say that my last RAID, a Sonnet DX800, used enterprise drives and has been bulletproof for five years. I wish you could buy the Pegasus2 with enterprise drives, but there are clearly a lot of satisfied Pegasus1 users out in the wild, chugging away on desktop drives. Personally, if I were buying a Pegasus2 (or any eight-drive RAID for that matter), I’d give myself some extra peace of mind and re-format it as a RAID 6. RAID 6 gives up a little speed and another drive of capacity, but uses two drives for redundancy. In other words, even if two drives fail, your data is still safe.

•   Speaking of reformatting, Promise gives you a user-friendly desktop app to reconfigure the Pegasus2 in its various RAID modes (0, 1, 5, 6, 10, 50, 60), report on drive health, and initiate rebuilding if a drive has to be replaced.

•   Promise also sells a 32 TB version of the R8 for $4,599, which is a pretty impressive price for 32TB of storage, all in a turnkey setup supported by one manufacturer. But there is a hitch: the eight 4 TB drives are slower than the drives of the 24 TB model (5900 rpm instead of the usual 7200 rpm), and Promise estimates that overall performance will be 10-15% slower than on the 24 TB model.

•   As for support, I called Promise’s tech support line multiple times with questions, and always got a knowledgeable rep within a few minutes. That kind of accessibility is reassuring.

Mild Quirks and an Annoying “Feature” (with Fix)
Everything went very smoothly for the three weeks that I worked with the Pegasus2, except for a couple of sleep-related quirks. On a couple of occasions, I would wake my Mac Pro from sleep and it would indicate that the Pegasus2 had not been ejected properly, reminding me to eject it before turning it off (though the RAID still woke up automatically and worked properly). I had used other Thunderbolt RAIDs that supported sleep, but never got this warning in the past, so it stood out as a Pegasus-only issue. Promise says it’s looking into it.

On one occasion, out of nearly 100 wake/sleep actions, the Pegasus2 didn’t wake from sleep at all with my Mac, and I had to reboot the Mac before the RAID became available as a volume again.

Finally, the Pegasus2 ships with an energy-saving feature that sleeps all drives after about five minutes of inactivity. That means if you take a phone call, write an email, or leave your editing app to work on a Photoshop graphic, your RAID will go to sleep. Then, when your computer tries to access the Pegasus files again, you’ll have to wait about 15 seconds for the RAID to spin up its drives. On the Mac Pro I used for testing, unchecking “Put hard drives to sleep when possible” in Energy Saver System Preferences had no effect, and neither did a similar setting found in Promise’s own RAID utility.

This 15-second wait is beyond annoying, and I’m not sure why Promise ships its RAID with this “feature” as the default. Fortunately, there’s a fix, which involves typing in a Terminal command. You can get the run-down at this Promise support link.

The energy-saver annoyance aside, the Pegasus2 is an impressive addition to the brave new(ish) Thunderbolt world — a user-friendly RAID with impressive speed, giant capacity and a relatively low price.

Helmut Kobler is a Los Angeles-based cameraman who also edits. Visit his website: